Issues installing .NET Framework 3.5 on a Windows 10 Computer

On some Dell Computers I have worked on, when attempting to download .NET Framework 3.5 components, the install program will give out an error and refuse to download the install package.  

This cannot be fixed by using the Net Framework 3.5 Offline Package.  Other install options through the Programs and Features control panel also fail, as do running commands manually.

I believe the problem is caused by the installer being unable to see the Windows Install files located in the …Sources\sxs folder that are used to install OS components.  This issue usually does not affect computers that have had Windows 10 installed manually and does not affect ALL Dell install images.  But it has become enough of a problem that I have had to create documentation to fix it.

This fix requires you to use a Windows 10 installation on an external drive.

Step 1: Plug in Windows 10 external drive – make note of the drive letter it is assigned to.

Step 2: Open Command Prompt as Administrator

Step 3: Run the following command: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:D:\x64\sources\sxs

Step 4: Source: refers to where on your Windows Install media you can locate …x64\Sources\sxs folder…

Step 5: DONE!

There are some other ways to do this, as well, but this seems to work the best.  One of the fixes I have run across involves downloading the ..Source\sxs.. folder from an unknown source.  That's a good way to get a virus!

I do not believe this is strictly a "DELL" issue.  I would look for this on computers where the manufacturer has a hidden partition containing the OS Recovery.  To date, I have not had this issue with computers where I have manually installed Windows 10.

Good luck!